The present invention relates to an undulated container for an undulated diaphragm and a diaphragm device, which may be used in a diaphragm accumulator, diaphragm pump, diaphragm actuator and so forth of the type in which a diaphragm is clamped between two container members each having an approximately bowl-shaped recess.
A diaphragm accumulator of the type in which a diaphragm is clamped between two container members each having an approximately bowl-shaped recess, as shown in the sectional view of FIG. 14, has heretofore been known. In the conventional diaphragm accumulator, a pan-shaped diaphragm 51 has a literally pan-shaped configuration as a whole. The central portion 2 of the pan-shaped diaphragm 51 has an approximately circular flat plate-shaped configuration. The outer periphery of the moving portion of the pan-shaped diaphragm 51 has an approximately frusto-conical configuration. The diaphragm accumulator includes a main body (first container member) 6 and a side plate (second container member) 7. The mutually opposing surfaces of the body 6 and the side plate 7 have approximately pan-shaped recesses 49 (on the body 6) and 50 (on the side plate 7) formed in the respective central portions. The body 6 has a stepped annular clamp portion 15 formed outwardly of the recess 49. Similarly, the side plate 7 has a stepped annular clamp portion 16 formed outwardly of the recess 50. The clamp portion 15 is formed with a first annular groove 17. The clamp portion 16 has a second annular groove 18 formed at a position which faces the first annular groove 17. The first and second annular grooves 17 and 18 are fitted with first and second seal members 11 and 12, respectively. The outer peripheral portion of the pan-shaped diaphragm 51 is clamped between the clamp portions 15 and 16. A plurality of bolts 22 are inserted into respective pairs of bolt holes 19 and 20, which are formed in the body 6 and the side plate 7, and nuts 23 are screwed onto the bolts 22, respectively. In this way, the outer peripheral portion of the pan-shaped diaphragm 51 is clamped between the clamp portions 15 and 16, and the area between the recesses 49 and 50 on the upper and lower sides of the pan-shaped diaphragm 51 is hermetically sealed by the first and second seal members 11 and 12. The space between the recess 50 of the side plate 7 and the pan-shaped diaphragm 51 is defined as a gas chamber (second chamber) 13, which is sealingly charged with a gas through a connecting opening 28 formed in the side plate 7. Similarly, the space between the recess 49 of the body 6 and the pan-shaped diaphragm 51 is defined as a fluid chamber (first chamber) 14, into which an external fluid is introduced through a supply and discharge opening 25 and a connecting opening 26, which are formed in the body 6.
In response to a change of the pressure in the fluid chamber 14, the pan-shaped diaphragm 51 is deflected to move toward the gas chamber 13 or the fluid chamber 14, and at an extremity of the deflection thereof, the pan-shaped diaphragm 51 comes in contact with either the recess 49 or 50. The position of the pan-shaped diaphragm 51 changes as shown by the alternate long and short dash lines in FIG. 14. That is, the pan-shaped diaphragm 51 can move from a position E where it completely comes in contact with the recess 49 to a position A where it completely comes in contact with the recess 50, via positions D, C and B. When the pan-shaped diaphragm 51 moves from the position E to the position A and also from the position E to the position B, most portions of the pan-shaped diaphragm 51 are irregularly deformed without coming in contact with the body 6. An example of the irregular deformation is local inversion of the direction of bending which occurs on the pan-shaped diaphragm 51 during movement. Local inversion of the bending direction is such a phenomenon that when the pan-shaped diaphragm 51 is moving toward the gas chamber 13 or the fluid chamber 14 in its entirety, the diaphragm 51 locally changes its shape from convex to concave or the reverse. On the other hand, when the pan-shaped diaphragm 51 moves from the position A to the position B and vice versa, the peripheral edge of the moving portion of the diaphragm 51 changes the bending direction from bending toward the recess 49 to bending toward the recess 50 or the reverse at the peripheral edge 5 of the gas and fluid chambers 13 and 14. Thus, irregular deformation such as local inversion of the bending direction of the pan-shaped diaphragm 51 occurs at many portions of the pan-shaped diaphragm 51, and a change of a curve from bending toward the recess 49 to bending toward the recess 50 or the reverse occurs at the peripheral edge of the moving portion of the pan-shaped diaphragm 51. Repetition of such deformation, particularly bending, causes the inflective portions to become fatigue. Consequently, the inflective portions rapidly deteriorate in strength and become easy to break.
A technique whereby the above-described disadvantage is partially overcome is disclosed in Japanese Utility Model Application Kokai No. 4-101801, which was laid open to public inspection in Japan on Sep. 2, 1992, although the disclosed technique is intended for a diaphragm accumulator of the type in which a diaphragm is attached to a spherical shell so as to face toward the fluid chamber.
In the diaphragm accumulator, the outer peripheral surface of the peripheral edge of a diaphragm (bladder) is brought into contact with the inner peripheral surface of a spherical body (shell), and an elastic mounting portion formed on the inner peripheral surface of the peripheral edge of the diaphragm is secured by a mounting member, thereby dividing the interior space of the body into a gas chamber and a liquid chamber by the diaphragm. In addition, an inward projection is formed on the inner peripheral surface of the body at the same distance from the elastic mounting portion, thereby reducing the distance between the inner peripheral surface of the body and at least the inner point of inflection of the inner and outer points of inflection of the inflective portion of an elastic material layer constituting the diaphragm, and thus increasing the buckling stress of the elastic material layer at at least the inner point of inflection of the inflective portion of the diaphragm. In doing so, the buckling stress is allowed to approach the rupture stress, thereby suppressing buckling of the elastic material layer.
In the diaphragm accumulator disclosed in the above publication, as the pressure in the liquid chamber lowers, the diaphragm moves toward and also along the above-described projection in the liquid chamber. In this case, the diaphragm is regularly deformed while being in contact with the inner surface of the body. However, after the diaphragm has passed the projection, irregular deformation occurs. When the diaphragm moves toward the gas chamber in response to an increase of the pressure in the liquid chamber, the diaphragm is irregularly deformed without coming in contact with the body. Irregular deformation includes, for example, local inversion of the bending direction of the diaphragm during movement as described above. Accordingly, the diaphragm locally changes its shape from convex to concave or the reverse. Repetition of local inversion of the bending direction causes the inflective portions to become fatigue. Consequently, the inflective portions rapidly deteriorate in strength and become easy to break.